Detlev Bremkamp told shareholders at a meeting that he and his German colleagues were no longer going to oppose their new Spanish masters, as they held a predictable majority of votes.
Yet he strongly criticised the ACS plan to fill the supervisory board with four of its own representatives, one from large shareholder Qatar Holding and three further ACS-chosen candidates.
“Hopefully that is not a signal that ACS is trying to take over complete control over the supervisory board in order to push through their own interests,” he said, adding the consequences would only be seen over the coming months and even years.
Bremkamp was joined in his departure from the board by Hans-Peter Keitel, Heinrich von Pierer and Wilhelm Simson.
He said that Thursday's departure, announced last month, of CEO Herbert Lütkestratkötter was not of his own volition.
“It was not the wish of Dr Lütkestratötter to leave the company, rather the major shareholder ACS valued his departure,” said Bremkamp.
Lütkestratötter used his final speech on Thursday to praise Hochtief and indirectly appeal to ACS to keep it going.
“The good reputation of Hochtief works to open doors in all international markets,” he said.
He and others who had opposed the hostile takeover of Hochtief by ACS fear the Spanish managers could break up the historic German firm. ACS owns more than 43 percent of Hochtief shares, and has increased its executive influence in the firm step-by-step over the last few months.